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Unformatted text preview: d and f travel to the left. Note that d and f are almost the same,
differing only by a phase shift. Any of the combinations a+d, a+f, b+d, b+f would
work. 8: (5 points) Standing waves are often produced in “cavities” like on a guitar string.
Explain why this is.
a: (3 points) What is required to produce standing waves and how is that condition met
inside such cavities?
Standing waves are produced when otherwise identical waves travel in opposite
directions. This condition is met in cavities when a wave started in the cavity
reflects back and forth off the boundaries, creating counter-propagating identical
waves of just the kind required.
b: (2 points) Why can oscillations of certain wavelengths exist on the string with large
amplitude while others cannot?
Waves which require a large amplitude oscillation at the ends of the string (which
are fixed in place) will rapidly lose any energy which they have, transferring it
into the frame which holds the string. As a result, the only waves which will
remain at large amplitude are those which have zero amplitude at the locations
where the string is fixed. These have = 2L/n. 9. (5 points) Monochromatic light with a wavelength of 450 nm passes through a single
narrow slit. On a screen 1.5 m away it produces the diffraction pattern shown below.
What is the width of the slit?
e. *35 m
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- Spring '08